MuleSource is different from SnapLogic in that it focuses on large-scale enterprise application integration, competing primarily with giants like Tibco and IBM. Mule is deployed in around 1100 large companies, including GE, Samsung, and TellMe. MLB.com uses Mule to help it track over 70,000 stats per year and distribute them to a large set of subscribers, a monumental task.

While much of Mulesource’s technology is free, the company offers a paid subscription service that includes 24/7 support and access to premium technologies.

Mulesource says that it has the bulk of its $4 million first round still sitting in the bank, but raised the additional capital to expand rapidly. The valuation was not disclosed. Original investors Hummer Winblad Venture Partners and Morgenthaler Ventures participated as well.

The company’s CEO, Dave Rosenberg, also occasionally writes for a blog that is popular within the open source community.